Thanks for confirming workability of the 245/45/18 all round the GT. The only variant on a couple of the combinations mentioned seem to be actual speed versus what the speedometer is telling us assuming 18"X 8" wheels. See link below and type in a few size variants. http://www.1010tires.com/tiresizecalculator.asp
Cam,Stall,LTH,CAI,Tune. Best time 12.7@110 1.9 60ft. Old Setup.
Dynoed 370whp 380wtrq(w/LTH,CAI,Tune)Best time 13.1@105 Old Setup.
New Daily 2016 GMC Sierra DC SLE 4x4: 5.3 Stock for now personal work truck.
For those that run with the GT edition the car came with 245/45/18. A switch using same 18" X 8" wide wheels to something like BF Goodrich g-force Sport Comp -2 in 255/45ZR/18 will yield a 1.312 % slower speed on the speedometer since the actual wheel diameter shrinks by 1.3%. Can anybody out there comment on any other material changes in operation of the car with this or more significant tire size changes ? For example, computer throwing any trouble codes, electronic brake assist or electronic stability control